102 FAMILIAR TREES 



The Hemlock Spruces (Tsuga) have but one central 

 resin-canal in the leaf, the true Spruces (Picea) have 

 one or two lateral ones, and the Douglas Fir (Psemlo- 

 tsuga), like the Silver Fir (Abies), has always two 

 lateral ones. The leaves of the Douglas Fir are 

 arranged singly and spirally as in both Spruces and 

 Firs, but though twisted so as to form a two-sided 

 spray, they do not lie as flat in two rows as do those 

 of the Silver Fir, but are rather in three or four 

 rows. They are of a bright shining green above, and 

 remain on for six or seven years. Three-quarters of 

 an inch to an inch and a quarter long, they are flat, 

 narrowly linear in outline, bending slightly upwards 

 at the apex, and varying considerably in the sharp- 

 ness or bluntness of that extremity. The stomata 

 are confined to two silvery lines, which are fainter 

 than those of the Silver Firs. In section the leaf is 

 elliptical, without the thinner areas on either side 

 of the midrib characteristic of Abies and Tsuga, or 

 the four-sidedness of Picea. The hypoderm varies, 

 but is generally only slightly developed ; there is 

 a large-celled mesophyll and a single undivided 

 vascular bundle, much as in Picea. 



The staminate flowers are mostly on the under 

 side of the twigs of the preceding year, forming 

 axillary egg-shaped masses. The pollen-grains have 

 not the air-bladders that occur in the Pines. 



The tree generally bears cones from about its 

 twenty-fifth year. These very distinctive features are 

 borne at the apex of the twig, hanging downwards, 

 first appearing in May, ripening in their first year, 

 and falling off whole. They are egg-shaped, from two 



